mpt3sas: Refcount sas_device objects and fix unsafe list usage

sas_device objects can be referenced concurrently throughout the driver.
We need a way to make sure threads can't delete them out from under each
other. This patch adds the refcount and refactors the code to use it.

Additionally, we cannot iterate over the sas_device_list without holding
the lock or we risk corrupting random memory if items are added or
deleted as we iterate. This patch refactors _scsih_probe_sas() to use
the sas_device_list in a safe way.

This patch is ported from the following mpt2sas driver commit
d224fe0d6097 ("mpt2sas: Refcount sas_device objects and fix unsafe list
usage").

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/scsi/mpt3sas/mpt3sas_transport.c b/drivers/scsi/mpt3sas/mpt3sas_transport.c
index 70fd019e7ee5..ca36d7ea0964 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_transport.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_transport.c
@@ -734,7 +734,7 @@ mpt3sas_transport_port_add(struct MPT3SAS_ADAPTER *ioc, u16 handle,
 	rphy->identify = mpt3sas_port->remote_identify;
 
 	if (mpt3sas_port->remote_identify.device_type == SAS_END_DEVICE) {
-		sas_device = mpt3sas_scsih_sas_device_find_by_sas_address(ioc,
+		sas_device = mpt3sas_get_sdev_by_addr(ioc,
 				    mpt3sas_port->remote_identify.sas_address);
 		if (!sas_device) {
 			dfailprintk(ioc, printk(MPT3SAS_FMT
@@ -750,8 +750,10 @@ mpt3sas_transport_port_add(struct MPT3SAS_ADAPTER *ioc, u16 handle,
 		    ioc->name, __FILE__, __LINE__, __func__);
 	}
 
-	if (mpt3sas_port->remote_identify.device_type == SAS_END_DEVICE)
+	if (mpt3sas_port->remote_identify.device_type == SAS_END_DEVICE) {
 		sas_device->pend_sas_rphy_add = 0;
+		sas_device_put(sas_device);
+	}
 
 	if ((ioc->logging_level & MPT_DEBUG_TRANSPORT))
 		dev_printk(KERN_INFO, &rphy->dev,
@@ -1324,15 +1326,17 @@ _transport_get_enclosure_identifier(struct sas_rphy *rphy, u64 *identifier)
 	int rc;
 
 	spin_lock_irqsave(&ioc->sas_device_lock, flags);
-	sas_device = mpt3sas_scsih_sas_device_find_by_sas_address(ioc,
+	sas_device = __mpt3sas_get_sdev_by_addr(ioc,
 	    rphy->identify.sas_address);
 	if (sas_device) {
 		*identifier = sas_device->enclosure_logical_id;
 		rc = 0;
+		sas_device_put(sas_device);
 	} else {
 		*identifier = 0;
 		rc = -ENXIO;
 	}
+
 	spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
 	return rc;
 }
@@ -1352,12 +1356,14 @@ _transport_get_bay_identifier(struct sas_rphy *rphy)
 	int rc;
 
 	spin_lock_irqsave(&ioc->sas_device_lock, flags);
-	sas_device = mpt3sas_scsih_sas_device_find_by_sas_address(ioc,
+	sas_device = __mpt3sas_get_sdev_by_addr(ioc,
 	    rphy->identify.sas_address);
-	if (sas_device)
+	if (sas_device) {
 		rc = sas_device->slot;
-	else
+		sas_device_put(sas_device);
+	} else {
 		rc = -ENXIO;
+	}
 	spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
 	return rc;
 }